Run the following command to update your package repositories:

sudo apt update

Install Node.js using the following command:

sudo apt-get install -y nodejs

Install Nginx to act as a reverse proxy for your Node.js application:

sudo apt-get install -y nginx

Install PM2 globally to manage your Node.js application:

sudo npm i -g pm2

Navigate to the Nginx sites-available directory and open the default configuration file for editing:

cd /etc/nginx/sites-available
sudo nano default

Inside the Nginx configuration file, add the following block to configure the reverse proxy for your API:

location /api {
    rewrite ^\/api\/(.*)$ /api/$1 break;
    proxy_pass http://localhost:8000;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}

After making changes to the Nginx configuration, restart Nginx to apply the changes:

sudo systemctl restart nginx

Navigate to your project directory and start your Node.js application using PM2. Replace server.js with the actual filename of your Node.js application:

cd /path/to/your/app
pm2 start server.js --name=Backend

If you need to restart your Node.js application managed by PM2, you can use the following command:

pm2 restart Backend

These steps should help you set up a Node.js backend API with Nginx and PM2 on your Debian-based Linux system. Make sure to customize the paths and filenames according to your specific project.